U.S. patent application number 10/568927 was filed with the patent office on 2007-08-16 for led light source.
This patent application is currently assigned to Schefenacker Vision Systmes USA Inc.. Invention is credited to Kyle P. Lucas, Ronald L. Steen.
Application Number | 20070187710 10/568927 |
Document ID | / |
Family ID | 34312237 |
Filed Date | 2007-08-16 |
United States Patent
Application |
20070187710 |
Kind Code |
A1 |
Steen; Ronald L. ; et
al. |
August 16, 2007 |
Led light source
Abstract
An LED unit (20) having increased light output. The LED unit
(20) includes a submount substrate (22) having a cavity (24). An
LED chip (30) is electrically mounted within the cavity (24) and a
phosphor layer (34) is deposited in the cavity (24) that converts
blue light from the LED chip (30) into white light suitable for a
vehicle headlight (10). The walls of the cavity (24) are metalized
(40) to increase the light output intensity. In one embodiment, a
clear protective layer (46) is deposited in the cavity (24) over
the phosphor layer (34).
Inventors: |
Steen; Ronald L.;
(Lindenhurst, IL) ; Lucas; Kyle P.; (Clawson,
MI) |
Correspondence
Address: |
WARN, HOFFMANN, MILLER & LALONE, .P.C
PO BOX 70098
ROCHESTER HILLS
MI
48307
US
|
Assignee: |
Schefenacker Vision Systmes USA
Inc.
1855 Busha Highway
Marysville
MI
48040
|
Family ID: |
34312237 |
Appl. No.: |
10/568927 |
Filed: |
September 7, 2004 |
PCT Filed: |
September 7, 2004 |
PCT NO: |
PCT/US04/28847 |
371 Date: |
March 20, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60500980 |
Sep 8, 2003 |
|
|
|
Current U.S.
Class: |
257/100 ;
257/E25.02; 257/E33.072 |
Current CPC
Class: |
B60Q 1/2696 20130101;
F21Y 2115/10 20160801; H01L 2924/0002 20130101; F21S 41/663
20180101; F21K 9/00 20130101; B60Q 1/00 20130101; H01L 33/483
20130101; H01L 33/505 20130101; F21S 41/155 20180101; H01L 25/0753
20130101; H01L 33/486 20130101; H01L 2924/00 20130101; H01L 33/508
20130101; H01L 2924/0002 20130101 |
Class at
Publication: |
257/100 |
International
Class: |
H01L 33/00 20060101
H01L033/00; H01L 29/24 20060101 H01L029/24 |
Claims
1. An LED unit comprising: a substrate including a cavity; at least
one LED chip mounted within the cavity; and a phosphor layer
deposited within the cavity and encapsulating the LED chip.
2. The unit according to claim 1 wherein a top surface of the
phosphor layer is substantially even with a top surface of the
substrate.
3. The unit according to claim 1 further comprising a clear layer
deposited in the cavity on top of the phosphor layer.
4. The unit according to claim 3 wherein a top surface of the clear
layer is substantially even with a top surface of the
substrate.
5. The unit according to claim 3 wherein the clear layer is
silicon.
6. The unit according to claim 1 wherein walls of the cavity are
metalized to provide an increased light reflection therefrom.
7. The unit according to claim 1 wherein walls of the cavity are
tapered.
8. The unit according to claim 1 further comprising a base
substrate that accommodates a plurality of LED units.
9. The unit according to claim 1 wherein the at least one LED chip
is a 1.times.1 mm square LED chip and the cavity is a 1.2.times.1.2
mm square cavity.
10. The unit according to claim 1 wherein the at least one LED chip
is two LED chips.
11. The unit according to claim 10 wherein the two LED chips are
square chips.
12. The unit according to claim 11 wherein the LED chips are
1.times.1 mm square LED chips.
13. The unit according to claim 1 wherein the LED unit is part of a
vehicle headlight.
14. A vehicle headlight comprising: a base substrate a cavity; and
a plurality of LED units mounted to the base substrate in a
predetermined pattern, each LED unit including a sub-mount
substrate having a cavity, each LED unit including at least one LED
chip mounted within the cavity and a phosphor layer deposited
within the cavity and encapsulating the LED chip.
15. The unit according to claim 14 wherein each LED unit further
includes a clear layer deposited in the cavity on top of the
phosphor layer.
16. The unit according to claim 14 wherein walls of each cavity are
metalized to provide an increased light reflection therefrom.
17. The unit according to claim 14 wherein walls of each cavity are
tapered.
18. The unit according to claim 14 wherein the at least one LED
chip is two LED chips.
19. A method of making an LED unit, said method comprising:
providing a substrate; forming a cavity in the substrate;
electrically mounting at least one LED chip within the cavity; and
depositing a phosphor layer within the cavity to encapsulate the
LED chip.
20. The method according to claim 19 further comprising depositing
a clear layer in the cavity on top of the phosphor layer.
21. The method according to claim 19 further comprising depositing
metal layer on walls of the cavity to increase light reflection
therefrom.
22. The method according to claim 19 wherein forming a cavity
includes forming walls of the cavity to be tapered.
23. The method according to claim 19 wherein mounting the at least
one LED chip includes mounting two LED chips within the cavity.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates generally to an LED light source and,
more particularly, to an LED light source that includes an LED chip
mounted within a cavity formed in a substrate, and a phosphor layer
deposited in the cavity to encapsulate the LED chip.
[0003] 2. Discussion of the Related Art
[0004] Vehicle styling and appearance provides significant and
important advantages for attracting customers. One recognized area
that is known to enhance vehicle attraction is the appearance and
design of the various vehicle lights, sometimes referred to as the
vehicle's jewels, including, but not limited to, headlights, tail
lights, turn signals, back-up lights, center high mounted stop
lamps (CHMSLs), running lights, fog lamps, side markers, etc. In
fact, modern vehicle designs pay close attention to the styling and
design of the vehicle lights.
[0005] Current vehicle lights employ various types of light sources
suitable for different designs and conditions. For example, vehicle
lighting designs have employed incandescent lamps, neon tubes,
halogen lamps, xenon lamps, etc. Some modern vehicle light designs
have employed light emitting diodes (LEDs) that are able to provide
various colors in an inexpensive and compact arrangement. LEDs
typically do not suffer from burn-out, and have good drive
characteristics, high luminance, high efficiency, high vibration
resistance and durability to endure repetitive on/off operations.
Therefore, LEDs have been attractive for vehicle lighting.
[0006] LEDs emit monochromatic light at wavelengths depending on
the doping characteristics of the LED semiconductor material.
Traditionally, the most efficient LEDs have emitted red light,
green light or blue light. It has heretofore not been possible to
provide an LED semiconductor material that emits white light.
However, various LED designs are available that convert colored
light to white light. One design employs a combination of red,
green and blue LEDs arranged close together. The light from the
LEDs is combined and diffused to provide the white light. However,
these types of LED designs have typically been limited because of
variances in tone, luminance and drive power of the different
LEDs.
[0007] Another white light LED design employs a colored light LED
and a fluorescent material that absorbs the colored light and emits
white light. U.S. Pat. No. 6,069,440, issued May 30, 2000 to
Shimizu et al., discloses a white light LED including a layer of
phosphor deposited over a blue light LED. The phosphor includes a
fluorescent that absorbs the blue wavelength light and emits white
light. In one particular design, the LED material is InGaN and the
phosphor layer includes an yttrium-aluminum-garnet fluorescent
material.
[0008] There is a push in the automotive industry to develop white
light LEDs so that LEDs can be used in vehicle headlights.
Important design concerns for vehicle headlights come into play
when using the existing technology for generating white light from
LED semiconductors, such as employing blue LEDs in combination with
a phosphor layer. Particularly, intensity and directional
considerations are important for the tightly regulated headlight
requirements. Further, providing a compact, efficient, low cost and
aesthetically pleasing LED package is necessary.
[0009] Improvements can be made in LED units to enhance or increase
the light output from the LEDs.
SUMMARY OF THE INVENTION
[0010] In accordance with the teachings of the present invention,
an LED unit is disclosed that provides an increased light output.
The LED unit includes a submount substrate mounted to a main
substrate. The submount substrate includes a cavity in which an LED
chip is electrically mounted. The remaining portion of the cavity
is filled with a phosphor material that converts blue light from
the LED chip to white light suitable for a vehicle headlight. The
sides of the cavity can be metalized so that the light emitted from
the LED unit is reflected therefrom.
[0011] Additional advantages and features of the present invention
will become apparent from the following description and appended
claims, taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a broken-away, perspective view of an LED headlamp
mounted to a vehicle body panel;
[0013] FIG. 2 is a top view of an LED unit, according to an
embodiment of the present invention;
[0014] FIG. 3 is a cross-sectional view through line 3-3 oft he LED
unit shown in FIG. 1;
[0015] FIG. 4 is a cross-sectional view of an LED unit, according
to another embodiment of the present invention; and
[0016] FIG. 5 is a top view of an LED unit, according to another
embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0017] The following discussion of the embodiments of the invention
directed to an LED light source is merely exemplary in nature, and
is in no way intended to limit the invention or its applications or
uses. For example, the following discussion describes the LED unit
as being applicable for a vehicle headlamp. However, as will be
appreciated by those skilled in the art, the LED unit of the
invention has application in many other environments.
[0018] FIG. 1 is a broken-away, perspective view of a vehicle
headlamp 10 mounted to a vehicle body panel 12. The vehicle
headlamp 10 includes a series of LED headlamp assemblies 14 mounted
to a common carrier 16. The LED assemblies 14 are enclosed within a
sealed compartment defined by an outer lens 18. The LED assemblies
14 include one or more LEDs that generate white light.
[0019] FIG. 2 is a top view and FIG. 3 is a cross-sectional view
through line 3-3 of an LED unit 20, according to an embodiment of
the present invention. The LED unit 20 can be one of several LED
units within each LED assembly 14. The LED unit 20 includes a
submount substrate 22 in which a cavity 24 has been formed by any
suitable process. In one embodiment, the submount substrate 22 is
made of aluminum nitride (AIN), however, this is by way of a
non-limiting example. The cavity 24 would be formed in the AIN
submount substrate 22 by a suitable masking and etching process, as
would be appreciated by those skilled in the art. The submount
substrate 12 is mounted to a main substrate 26, where several other
LED units (not shown) can be mounted to form an LED unit array. In
one embodiment, the main substrate 26 is the carrier 16 of the
headlamp 10.
[0020] The LED unit 20 includes an LED chip 30 electrically mounted
within the cavity 24. In this embodiment, the LED chip 30 is
mounted to the substrate 22 by "chip-on-board" technology that
provides an electrical connection to the submount substrate 22 by
solder or stud bumps 32. Once the LED chip 30 is mounted within the
cavity 24, a phosphor layer 34 is deposited within the cavity 24 to
completely encapsulate the LED chip 30. In one embodiment, phosphor
is placed on a top surface 36 of the submount substrate 22, and
then a squeegee is used to push it into the cavity 24 so a top
surface 38 of the phosphor layer 34 is flushed with the top surface
36 of the submount substrate 22. The opening of the cavity 24
defines the source size of the LED unit 20.
[0021] In one embodiment, the walls of the cavity 24 are metalized
with a suitable metal layer 40, such as aluminum, silver, etc. This
provides better light scattering and reflection for higher beam
output. Also, in this embodiment, the walls of the cavity 24 are
straight, i.e., at 90.degree. relative to the top surface 36.
However, in alternate designs, the walls of the cavity 24 can be
flared out at a predetermined angle to provide a desirable light
reflection therefrom.
[0022] In this embodiment, the LED 30 emits blue light, and the
phosphor layer 34 converts the blue light to white light in a
manner that is well known to those skilled in the art. The
thickness of the phosphor layer 34 defines the color of the light
emitted from the unit 20. Particularly, if the thickness of the
phosphor layer 34 is too thin, then the light will be more yellow.
Likewise, if the thickness of the phosphor layer 34 is too thick,
then the light will be more blue. Alternately, the LED 30 can be
replaced with a UV LED and the phosphor layer 34 can be a red,
green, blue phosphor layer to provide the white light.
[0023] The cavity 24 provides a well-defined shape for the phosphor
layer 34, where the sides of the phosphor layer 34 do not affect
the directionality of the light beam. Further, by confining the
phosphor layer 34 in the cavity 24, the light from the LED chip 30
is homogenized to even out the light output. Also, the light output
of the LED chip 30 is easier to model. By controlling the shape,
size and dimensions of the phosphor layer 34 within the cavity 24,
the optical quality of the light beam is increased.
[0024] In one embodiment, the submount substrate 22 is
approximately 2.times.2 mm square having a height of about 1.05 mm.
The cavity 24 is a 1.2.times.1.2 mm square having a depth of
approximately 0.7 mm. The LED chip 30 is approximately 1.times.1 mm
square.
[0025] In an alternate embodiment, the cavity 24 can be only
partially filled with the phosphor layer 34 to the desired
thickness. FIG. 4 is a cross-sectional view of an LED unit 44
depicting this embodiment of the invention, where like elements are
identified by the same reference numeral. The LED unit 44 includes
a clear layer 46 deposited in the cavity 24 on top of the phosphor
layer 34. The clear layer 46 can be a silicon layer, or any other
suitable material, that provides a protective and inactive layer,
but seals the phosphor layer 34 from the environment.
[0026] In order to increase the output intensity of the LED unit
20, it is possible to provide more than one LED chip in the cavity
24. FIG. 5 is a top view of an LED unit 50, similar to the LED unit
20, that includes two LED chips 52 and 54 formed within a cavity 56
of a submount substrate 58. A phosphor layer 60 fills the cavity 56
to encapsulate both of the LED chips 52 and 54. In this embodiment,
the chips 52 and 54 are both 1.times.1 mm square, and the length of
the cavity 56 is increased to 2.3 mm to accommodate both of the
chips 52 and 54.
[0027] The foregoing discussion discloses and describes merely
exemplary embodiments of the present invention. One skilled in the
art will readily recognize from such discussion and from the
accompanying drawings and claims, that various changes,
modifications and variations can be made therein without departing
from the spirit and scope of the invention as defined in the
following claims.
* * * * *